Conference Vancouver, B.C. June 11, 2001
Speakers
Dr Sutcliffe: I am going to go back to colorectal cancer and I believe that we have two clear indications recommended: One in colorectal cancer is the detection of recurrence where conventional imaging methods are negative or equivocal and there is suspicion of recurrence either as elevated CEA or by virtue of patient symptoms.
Dr Conti: Two points just to remember:
Dr Sutcliffe: Helen, do you have any comment on that? Any comment from the floor on that particular question?
Dr Conti: I didn’t think so.
Dr Sutcliffe: From the panel?
Dr Shreve: I guess one of the issues is, do you do any imaging staging for patients with primary colon cancer before the operation and in some cases the surgeons go ahead and operate and do operative staging before a CT scan is even done—I guess the question would be if you are going to do a CT scan for staging why not do a PET scan? That would probably be a better way to put it.
Dr Conti: I think if you are asking an anatomical question where in terms of surgical planning you need the anatomy then you do the CT scan irrespective of PET, but the issue really comes down to if you are willing to take the chance to rely on PET to detect recurrent disease—that might be surgically respectable. That is the same cancer in fact, that you started with—that you could have staged initially, that you could have made a difference in the initial management of the patient in terms of the original surgical approach perhaps? It may have had that liver metastasis in the first place, that could have been resected when it was only one instead of three say, at the time of recurrence. So, given the fact that it is the most sensitive test that we have, given the fact that is for colorectal cancer, given the fact that it has shown efficacy in terms of its utility in deciding surgery or no surgery in the recurrent population. You should consider using it in terms of treatment planning up front after the initial diagnosis—not necessarily to make the diagnosis in colorectal cancer but to stage the patient.
Dr Sutcliffe: So Peter you have agreed with the detection of recurrent indication but you are broadening that to say pre-operative staging prior to further management would also be the appropriate indication.
Dr Anderson: That is very interesting suggestion that you have made. Is there any evidence that this has been done? Where do you draw the line in saying that the patient who has stage 1, early stage colorectal cancer, their chance of recurrence is very low, what is the evidence? Which group of patients would you do these PET staging investigations for?
Dr Conti: The answer is unknown—that is why I am asking you as a group. Are you willing to take the chance, based on the fact that the evidence is very strong in the other population? It is almost unequivocal that PET is useful in the issue of determining whether someone should be re-resected with recurrence, and given the fact that it is probably the same cancer, given the fact that there is avid FDG uptake in colorectal cancer, and given the fact that it is a surgically treatable disease, and if there was disease, that was resectable early on; it could have an impact on patient management and care and perhaps outcome. Why not do it that way, despite the absence of specific literature?
Dr Anderson: Perhaps a better question would be: why does one not do a study looking at this particular question rather than just adopting it?
Dr Conti: The answer to that is that we do it in clinical practice, many of us already and we are beyond worrying about this, we are into something else now; that is what has happened. A lot of the PET literature is, it is not necessarily information that is published anymore.
People have moved beyond doing some of these indications—they have adopted them as routine procedures, they are moving into other areas of investigation in the academic centres. There is no driving force to do something that you find already clinically efficacious to necessarily publish a prospective trial to prove it, the procedures have moved on.
Dr Wahl: Well I think that still it is probably publishable in primary colorectal cancer. Exactly what the role is I, there is not much literature there, much more literature in recurrent, and you know I think, certainly our colorectal surgeons are interested in this possibility, particularly the higher the Dukes Stage, the more likely it is you have metastases to other tissues and potentially the liver, and clearly if you are going in to do supposedly curative surgery and lesions are in the liver and you don’t know it, it is kind of not optimal. So there probably is a point where the lesion becomes high enough risk that it would have a high yield of being useful in this less invasive primary colorectal, it is probably not going to be a very high yield and certainly the issues of detecting small little metastases are going to remain, I mean the physical limitations of detecting these lesions will remain with PET which will be better staged surgically. So I think Peter that you are right and a reasonable thing to do, but I also would agree that doing a few more studies on it would be probably pretty useful because most people are not using it primarily for staging.
Dr Sutcliffe: I suspect Peter that no one has a philosophical or conceptual difference, we know that with a very conservative funding body which we will engage, the absence of evidence will be a detriment to getting that done. So we have discussed that indication. The other indication put forward was staging in patients who have potentially resectable recurrence; is there any dispute on that or concerns with that indication?
Dr Baum: I just would like to stress from our own data that in Frankfurt where we had several hundred of patients that were studied before liver resection of metastasis that it is a very good method of detecting extra hepatic disease especially if you plan for regional chemotherapy on let’s say complicated regional resection of liver metastasis, central liver metastasis which are high risk and so on. It is a very good method to look at extra hepatic disease. In quite a number of patients you find extra hepatic involvement which was previously not known I still have a small criticism let’s say, to the way you presented the role of PET in colorectal cancer, you said several times that there is not much data or very small data and so on, I would like, I don’t know if you know this, this is the Supplement of the Journal of Nuclear Medicine, which just appeared in May. I would just like to make a citation of that: This is the summary of 1387 patients, 2444 lesions and sensitivity was 94% and 87%. I mean one might doubt if this is useful to make these summaries and meta-analysis but it is not a small number, several studies here include patient numbers of more than 100 and I think that it is a very good body of evidence in colorectal cancer and I was responsible in 1997 for the German Consensus Committee on colorectal cancer and at that time we already decided that there was enough data to justify that it is good for searching for recurrence and staging for patients who are planned for major surgeries so since then the data are much more robust.
Floor (original in Head and Neck Discussion):
I just want to go back to colorectal, for a minute, the one recommendation that it be used in patients who are asymptomatic but have an elevation of their tumour marker—there have been a number of studies published showing that there isn’t any really definite benefit to following patients with tumour markers and it was my understanding that we are trying to educate the mostly community physicians to stop ordering CEAs, stop ordering CA15.3s, 19-9s in patients who have been treated for their disease. So I am just wondering how that recommendation ties in with that because I mean I certainly have been in that situation before where I have had consults coming in from family doctors that someone who had a breast cancer or colon cancer resected a few years ago and now their marker is going up and they end up with a million dollar work up and you don’t find anything.
Dr Baum: I think that one of the main reasons to doubt about the usefulness of tumour markers was the lead-time of tumour markers because conventional imaging was not able to find and localize the tumour. Now I think this has exactly changed by application of FDG-PET at least in colorectal cancer, in our series and this involved several hundred patients there was if I remember only two patients with an elevated CEA where the PET scan was negative and this turned out to be brain metastasis of colorectal cancer which is quite rare, but where we missed it, but all the others had positive lesions so in my view it is very important to do tumour markers in the follow up of high risk patients especially Dukes C and so on, and to detect early disease especially single liver metastasis, which can be resected or single lung metastasis which can be seen and resected.